alloxan Syllabification: (al·lox·an)Pronunciation: /əˈläksən/Definition of alloxan noun Chemistry an acidic compound obtained by the oxidation of uric acid and isolated as an efflorescent crystalline hydrate. Chemical formula: C4H2N2O4 Origin: mid 19th century: from all(antoin) + ox(alic) + -analloxan in other Oxford dictionaries Definition of alloxan in the British & World English dictionary